Aqueous solutions of ferric chloride (FeCl3) are commonly used as flocculating agents for treatment of water, for hydrogen sulfide control, struvite control, sludge conditioning, color removal, phosphate removal, heavy metal removal, lime softening applications, and the like. For water treatment applications, the trivalent iron functions exceptionally well for both potable and wastewater clarification. Solutions containing ferric chloride can be prepared in a variety of ways. For example, ferric chloride solutions can be produced by oxidation of ferrous chloride using oxygen (O2) or chlorine (Cl2); by dissolution of ferric oxide with hydrochloric acid; and the like. These iron solutions are typically supplied with an iron concentration of less than 15 weight percent because at higher iron concentrations, precipitation can result especially when the ferric chloride solution is subjected to relatively low temperatures of about 0° C. or less and/or are not solution stabilized with hydrochloric acid.
Many of the processes for manufacturing ferric chloride use hydrochloric acid as a reagent in the reaction. For example, the reaction of ferric oxide with hydrochloric acid to form ferric chloride can be quantified as follows:1Fe2O3+6HCl2FeCl3+3H2O
The hydrochloric acid and ferric oxide react to form reaction products including ferric chloride, water, and residuals including unreacted hydrochloric acid and unreacted ferric oxide. The amount of unreacted hydrochloric acid in the product is typically on the order of a few weight percent.
In view of economies of scale, it would be desirable and a significant commercial advantage to define a process and solution composition that provides a solution with an increased iron content